1. Technical Field
The present invention relates to a multi-pressure radial turbine system that recovers energy from a low- or intermediate-temperature fluid and a high-temperature, high-pressure fluid and converts the energy into rotational power.
2. Description of the Related Art
In conventional power generation, energy is recovered from a low- or intermediate-temperature fluid and a high-temperature, high-pressure fluid, the energy is converted into rotational power, and the rotational power is used to drive a generator. Known generation systems of this type include, for example, a binary-cycle power-generation system (hereinbelow referred to as a “binary power generator”). Even when, for example, geothermal power generation is impossible because the temperature and pressure under the ground are low and hence it is only possible to obtain hot water, this binary power generator boils a medium having a lower boiling point than water (a low-boiling point fluid), such as ammonia, pentane, or chlorofluorocarbon, using the hot water to rotate a turbine with the vapor of the low-boiling point fluid.
A conventional binary power generator will be briefly described with reference to FIGS. 7 and 8.
FIG. 7 is a block diagram showing a configuration example of a binary power generator Ba. In the illustrated binary power generator Ba, a cycle circuit, through which a heating medium circulates while repeatedly changing its state, includes a pump 11 for pressurizing the heating medium, an evaporator 13 that receives heat from a high-temperature heat source and vaporizes the heating medium, a turbine 15 that expands the high-pressure, high-temperature heating medium vapor and converts the heat energy into rotational power, and a condenser 17 that condenses the low-temperature heating medium, resulting after expanding and releasing its energy, into liquid again. These devices are connected by pipes to form a closed circuit.
In this case, air or water at atmospheric temperature, such as air, river water, or sea water, is used as a low-temperature heat source (temperature level TC) that absorbs heat in the condenser 17. Furthermore, in ocean heat energy conversion (OTEC), low-temperature sea water near the seabed is used as the low-temperature heat source.
On the other hand, examples of the high-temperature heat source (temperature level TW) include high-temperature, high-pressure fluids discharged from various industrial plants, fluids discharged from ship or vehicle power sources, such as exhaust gas, and heat source fluids used in geothermal power generation and ocean heat energy conversion. When the temperature level of the high-temperature heat source, TW, is about several tens to 200° C., a chlorofluorocarbon, a chlorofluorocarbon substitute, a next-generation chlorofluorocarbon, or an organic medium having a critical temperature of approximately 100° C. to 200° C. is used as the heating medium, and at higher temperatures, water is used.
The T-S diagram in FIG. 8 shows a saturation line of the above-described heating medium.
The output of the turbine 15 obtained by the illustrated cycle is used as power-generation motive power for driving the generator 19. That is, the heating medium circulating while exchanging heat with the high-temperature heat source at the temperature level TW and with the low-temperature heat source at the temperature level TC expands in the turbine 15 (expansion), where it does work, i.e., drives the generator 19, and this work is used as electric power.
Accordingly, it is designed to generate maximum electric power using the illustrated binary cycle when a high-temperature heat source having a low or intermediate temperature and a low-temperature heat source are given, and the main parameters are the evaporating pressure P1 and the condensing pressure P2 of the heating medium. Selecting appropriate pressure settings of the evaporating pressure P1 and the condensing pressure P2 is usually performed in industrial processes.
Furthermore, in a radial turbine using a swirling fluid that has a radial flow velocity component as the main component and that flows into a turbine wheel and axially discharging the flow resulting after converting the swirling energy of the flow into the rotational power and releasing energy, the fluid pressure is split into a plurality of flow paths in the turbine, each of the flow paths is provided with a turbine rotor blade inlet, and the radii of the turbine rotor blade inlets are differentiated from one another (see Japanese Unexamined Patent Application, Publication No. Sho 63-302134; Japanese Translation of PCT International Application, Publication No. 2008-503685; and Japanese Unexamined Utility Model Application, Publication No. Sho 61-202601).